<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			console.log("日志");
			var a ;
			console.log(a);
			
			var s = "hello";
			var n = 3.14;
			var b = true;
			console.log(s);
			console.log(n);
			console.log(b);

			console.log(n.toString());
			console.log(b.toString());
			console.log(parseInt("3.14"));
			console.log(parseFloat("3.14"));


		</script>
	</body>
</html>